How do you measure voltage and current in high voltage distribution?
Voltage – a high voltage probe. This consists of a chain of resistors such that the total rated voltage exceeds the voltage to be measured. For example, a chain of 100 resistors each rated at 500 volts would give a 50kV probe. Most of the 1/2 watt cermet resistors have a voltage rating of 500V or so. This rating is limited by arcing over inside the resistor. The resistor chain has to be immersed in a high dielectric strength medium, such as epoxy, silicone, or freon gas. This prevents arcing between resistors. The outside of the probe has to have a series of discs on it so as to avoid tracking of arcs down the outside of the probe. There is also a suitable resistor to ground so as to produce a known attenuation, generally 1000:1. The design and testing of high voltage probes is very difficult. Usually, once one has been invented, people stick with it. There are very few manufacturers of these.
